Stop bath

The stop bath (also interrupter) is an acidic solution, which serves to interrupt the development process in photographic film or paper. This is achieved by the basic developer is neutralized by the acid in a stop bath.

For stop baths come, due to the chemical characteristics of the subsequent fixing bath, only acidic solutions having a pH value of 4 to 6 in question. Probably the most commonly used bathroom is a 2% acetic acid. But be filled with water to 1000 ml 20 ml acetic acid (glacial). When dealing with glacial acetic acid with caution. He etches much the skin and solidifies at 12 ° C. Skin contact with rigid glacial acetic acid should be avoided.

Equally effective, but without the typical odor of acetic acid, a weak citric acid.

Require the use of an acidic stop bath only when an acidic fixer to be used in order to neutralize the basic developer entrained and thus to extend the life of the fixing bath. Otherwise, a short intermediate washing enough to stop the development process.

Films and papers should be no longer than 60 seconds in the stop bath are treated as they acidify otherwise. In the final wash -acidification makes it difficult to wash out the silver salts.

• Darkroom
• Photo Lab Technology
• Photochemistry